The present invention relates to a method of forming a pneumatic tire for an automobile.
In general, pneumatic tires for automobiles are manufactured as follows: Namely, the inner surface of a tire is formed of a toroidal carcass ply on which an inner liner is lined. The crown portion of the carcass ply is covered with a BT band composed of a belt and a tread rubber, whereas portions extending from the side surfaces of the carcass ply to the outer peripheral BT band are covered with side rubbers. The green tire with such a construction is first formed of a green rubber, and is then vulcanized.
Conventionally, the formation of the green tire described above has been carried out, for example, in such a procedure as shown in FIG. 1. First, as shown in (A) of this figure, a carcass ply 02 is wound around a first forming drum 01 in a cylindrical shape, and bead wires 03 are mounted at both the end portions of the carcass ply 02, and subsequetntly, the carcass ply 02 is folded in such a manner as to wrap these bead wires 03. Next, as shown in (B), side rubbers 04 are wound and stuck around both the folded ends. In this case, a sheet 05 made from polyethylene or the like (hereinafter, referred to as "polysheet") is interposed between each of the side rubbers 04 and the carcass ply 02 such that the inner peripheral surface portion of the side rubber 04 is not adhesively bonded on the carcass ply 02.
The carcass body thus formed is removed from the first forming drum 01, and is transferred onto a second forming drum 06 (see (D)). The second forming drum 06 is so constructed that a pair of drum bodies 06a and 06b with the end surfaces being opposed to each other are connected to each other by means of a bladder 07. A pressurized fluid is supplied within the bladder 07 and both the drum bodies 06a and 06b are moved so as to be close to each other, so that the bladder 07 is expanded/deformed in a toroidal shape as shown in (E).
As shown in (C), a BT band 011 composed of a belt 09 and a tread 010 is separately formed on a BT drum 08. The BT band 011 is transferred by use of a transfer ring 012, and is positioned over the outer peripheral portion of the second forming drum 06 on which the above carcass body is mounted (see (D)).
As shown in (E), the above side rubbers 04 are raised outward to remove the polysheets 05, and in such a state the bladder 07 is expanded as described above. Accompanied with the expansion of the bladder 07, the carcass ply 02 is deformed in a toroidal shape, and is press-contacted with the BT band 011 positioned on the outer peripheral portion side of the carcass ply 02.
As shown in (F), the BT band 011 is bent along the carcass ply 02 by a stitcher (not shown), and is adhesively bonded therewith. Subsequently, as shown in (G), folding stitchers 013 are moved in the directions shown by the arrows, so that the side rubbers 04 are press-bonded on the side surfaces of the carcass ply 02 and the side edge portions of the BT band 011.
In the conventional method of forming a green tire described above, when the side rubbers 04 are wound around the first forming drum 01, the polysheets 05 must be wound together with the side rubbers 04,and further, the polysheets 05 must be removed prior to the process of expanding/deforming the carcass ply 02. This needs the excessive process and lengthens the time required for the forming work.
Moreover, since the polysheet 05 is reused, the recover of the polysheet takes a lot of labor, and a reproducing apparatus must be installed.
Additionally, when the polysheet 05 is removed, the side rubber 04 is raised, as a result of which the side rubber 04 is deformed. This often causes the failure in the shape of the side rubber after being press-bonded on the side surface of the tire.